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, Australian Centre for Geomechanics, Perth, pp. 437-446.
Planning for the closure of Energy Resources of Australia Ltd’s (ERA) Ranger uranium mine requires an understanding of potentialimpacts to water quality in adjacent receiving waters. Potential mine impacts need to be evaluated in the context of the Commonwealth environmental requirements, which include possible incorporation of the site into Kakadu National Park; onsite (i.e. within the Ranger Project Area) impacts that are as low as reasonably achievable (ALARA); and protection of the people, ecosystem, and World Heritage and Ramsar wetland values of the surrounds. Adopting best practicable technology (BPT) is also required.
Water quality guideline values have been developed to support the management goal of achieving no change to biodiversity outside the Ranger Project Area. Guideline values to support the management goal of ensuring impacts onsite are ALARA, while still protecting the offsite values, have not been obtained. An agreed framework is needed to understand the changes that might occur at different concentrations of contaminants in the Ranger Project Area so that stakeholders can consider and assess whether such changes are ALARA and protective of the downstream values. The national water quality guidelines provide a framework for assessing remediation programs, while, under the environmental requirements, the closure of Ranger must be assessed using a BPT framework. Consideration of alternative management options, community, and environmental and cost aspects are common to both frameworks.
Additionally, ERA is working with consultants (BMT) and stakeholders to develop a risk-based vulnerability assessment framework to identify ecological and cultural endpoints for the environmental requirements, considering impact components such as duration, geographic extent and resilience, to determine how different concentrations of magnesium—potentially the most restrictive contaminant of concern—might affect these endpoints.
This paper describes an initial review of how these frameworks may be used to appraise the mine closure strategy’s compliance with the environmental requirements. The review can inform discussions with stakeholders on a suitable approach for setting water quality objectives for closure.
Keywords: water quality objectives, guidelines, ALARA, BPT, vulnerability assessment, mine closure
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